Delivering speed and safety to pipe weld testing

Cutaway view of 4-inch GripTight Isolation plug in pipe. Image supplied by Curtiss-Wright EST Group.

Conventional flange-to-pipe weld testing often carries high costs and risks of downtime and delays, disposal challenges and potentially dangerous work conditions. Curtiss-Wright EST Group developed its GripTight® Isolation Plug to resolve these challenges and keep workers safer.

The GripTight Isolation Plug is a one-tool solution that positively isolates and monitors potentially hazardous or explosive vapors upstream of a welding job, before hydrotesting the new weld connection. The GripTight Isolation Plug features the GripTight gripper technology, a proven system with a 20-year track record of successful use in EST Group’s GripTight Test Plugs.

The gripper system is designed for reliable sealing and adheres to the principle, “the greater the pressure, the greater the grip”. If a faulty valve should cause a rapid increase in the upstream pressure, the grippers use that pressure to increase their grip on the pipe’s inner diameter (ID) wall The grippers hold the GripTight Isolation Plug in place and withstand the full rated line pressure up to 103 BarG, thus preventing a failure that could damage the line or lead to serious injury for the onsite work crew.

A two-seal system

The GripTight Isolation Plug is built on the functionality of the proven Double Block and Bleed (DBB) Test Plug, a two-seal plug that revolutionises how pipe connections are isolated and tested.

The DBB Test Plug has a dual port design that allows gas or water to be introduced to the cavity section between the two seals through the fill port. Air is evacuated through the vent port, resulting in a safe, positive pressure barrier between the hot work and any residual upstream gases.

This cavity is pressurised and constantly monitored. Any decrease in cavity pressure, which might indicate a leak, is detected instantaneously. This allows the operator to stop the welding operation and immediately attend to the pressure drop to prevent the possibility of an explosion or fire.

The plug’s dual port system also allows water (or other medium) to be circulated between the seals, providing enhanced cooling capabilities during pre/post weld procedures. This cooling feature can enhance safety when working in areas with tight space restrictions that require the plug to be set close the weld area.

The GripTight Isolation Plug is also designed for use in seamless and welded pipe.

In situations in which seam-welded pipe is used or where corrosion, pitting or scale is present, the pipe’s ID may require some preparation before the plug is installed. With an increased clearance, the plug can be positioned over a weld for testing, even when a slight weld intrusion is present on the ID of the pipe.

Pressure testing

Once the welding is complete and the weld area has cooled to below 82°C, the seals are released, and the plug can be moved to reposition the isolation cavity over the weld. The plug is then reset and pressurised to test the integrity of the weld, up to a test pressure of 155 BarG. Pressure tests can be completed in as little as 10 minutes from insertion to removal.

The GripTight Isolation Plug also permits pressure testing with significantly less water than traditional pressure test methods. For example, using a traditional blind flange to test a weld in a 1000-ft length of 12-inch, schedule 40 pipe, would require filling the entire line with approximately 5800 gallons of water.

Using the GripTight Isolation Plug to test that same weld requires less than a gallon of water. This not only significantly reduces fill time and minimises the challenges associated with disposing of large volumes of potentially contaminated water, but it also helps get the line back into service more quickly.

GripTight Isolation Plug 42-Inch. Image supplied by Curtiss-Wright EST Group.
GripTight Isolation Plug 42-Inch. Image supplied by Curtiss-Wright EST Group.

Reliability and availability

Each GripTight Isolation Plug is manufactured in an ISO 9001:2015 registered facility
and is designed to meet ASME Boiler and Pressure Vessel Codes.

The plugs also meet ANSI N45.2, NQA-1, and 10 CFR 50 Appendix B program requirements.

The GripTight Isolation Plug is available in a wide size range – from ¾-inches to 48-inches NPS (DN20 to DN1200) – with larger sizes available upon request.

The plug’s lightweight aluminum and steel construction makes it easy to transport and install, oftentimes circumventing the necessity of cranes or other lifting devices. GripTight Isolation Plugs come standard with urethane seals but can be custom built with alternate material upon request.

Curtiss-Wright EST Group can supply GripTight plugs to plants, shipyards, and refineries across the Gulf Coast quickly, thanks to a Houston-based distribution network that stocks plugs of various sizes and specifications.

The rapid response of a local supplier is critical in unplanned or emergency situations where maintenance needs to be completed safely and efficiently. A plug can be express shipped to the site to allow the operator to fix the problem and get the pipe back in service quickly.

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This article featured in the January edition of The Australian Pipeliner. 

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